Sealing closure for fuses or the like



June 24-, 1941. w F 2,247,084

SEALING CLOSURE FOR FUSES OR THE LIKE Filed Dec. 2, 1938 Inventor:

Robert W. Goff.

Hi Attorrweg.

Patenteci june 24, 194i Robert W. Goff, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 2, 1938, Serial No. 243,609

Claims.

The present invention relates to sealing closures and has for a general object the provision of an improved form and arrangement of closure for sealing an open end of a tubular casing of a fuse or like electric device.

One of the more specific objects of the invention is to provide a simple, economical, and at the same time reliable sealing closure for use in the construction of enclosures for fuses of the cartridge type. 1

There are available enclosed fuses of the socalled current limiting type, employing an inert arc-quenching filler medium such as sand or granular quartz, which have certain peculiar and very desirable operational characteristics, one of which being that current interruption is effected without development of any appreciable gas pressure and without discharge of gas or solid particles. However, for application of fuses of this type under oil or other liquid insulating medium, it is important that they be provided with an enclosure which eifectively excludes the liquid medium from the interior of the enclosure. Other- Wise, contamination of the sand or other inert filler by the liquid medium would impair the arcquenching efiiciency of the filler and might result also in building up of dangerous pressures within the fuse enclosure due to vaporization of the liquid medium. Considerable diiificulty has been encountered in the provision of a satisfactory enclosure for such inert filler current limiting fuses when it is desired to apply the same under liquid insulating medium,

It is therefore a further object of the invention to provide a sealing closure for use in the construction of liquid-tight enclosures for fuses of the current limiting type above referred to and designed for operation under oil or other liquid insulating medium. My invention makes possible the provision of an economical liquid-tight fuse enclosure which permanently and effectively excludes oil or other liquid insulating medium from the internal elements of the fuse and which at the same time provides for making proper electric connection to the fusible element within the enclosure.

Other objects and the details of that which I consider to be my invention will be readily understood from the following description and the claims appended thereto, taken in conjunction with the accompanying drawing wherein is i1- lustrated an exemplary embodiment of the invention as employed in the construction of a liquidtight enclosure for an inert filler current limiting fuse. Fig. 1 of the drawing shows a longitudinal section of the exemplary fuse construction and Fig. 2 is an exploded view of certain elements of the fuse of Fig. 1.

The illustrated fuse has a casing iii of openended tubular form and constructed of fibrous or other suitable insulating material. Screwthreaded respectively on the opposite ends of the casing are closure caps l l, of brass, copper, or the like, which serve as terminals for the fuse and which have central screw-threaded sockets 12 providing for the making of electric connection thereto. In the assembly of the caps on the casing it is preferable, though not essential, that a suitable cement be applied to the threads of the caps'and casing so as more effectively to tighten and'seal the junctions therebetween. Within the casing is a fuse link it. The opposite ends of this fuse link are secured respectively to fuse link attachment or terminal plates is by insertion of the fuse link ends through slots 55 in the terminal plates and by bending over the outwardly projecting portions of the fuse link ends and soldering these bent-over portions to the terminal plates, as indicated at it. Plates it are constructed of copper or brass and are pressed into annular recesses l 7 respectively in opposite ends of the easing. The peripheries of the plates are provided With knurling or serrations l8 which bite into the wallsof recesses l'l so as to prevent turning of the plates relative to the casing. The interior of the casing is filled with an inert arc-quenching material [9 such as sand or granular quartz.

In order to seal the ends or" casin lil, there are interposed between the plates it and the caps 22, respectivelyv at the opposite e.-ds of the casing, annular washers or retaining rings 25 and annular gaskets 2i. The washers are constructed of relatively soft and deformable copper and serve to provide electric connection between plates id and caps l2. Also, each of the washers has a generally U-shaped cross-section, as will be seen best from Fig. 1, so as to provide an annular channel which opens outwardly, or in other words substantially normal to the axis of the washer. Annular gaskets 2t are constructed of asbestos, synthetic rubber, or other suitable compressible and deformable material which is not attacked by oil or other liquid insulating medium in which the fuse may be immersed, and the gaskets are seated respectively in the annular channels of the retaining rings or washers 2%. As will be noted from the drawing, one side of the channel in each of the washers 2@ has less width than the other side and the Washers are arranged in such manner that the narrow sides of the channels are adjacent to plates [4, so that a part of the gaskets is exposed for engagement with plates 14 and the ends of easing l0.

Gaps H are screwed tightly on to the ends of easing In so as to compress gaskets 21 and washers 20. Compression of washers 20 and gaskets 2| forces the exposed part of the inner sides of the gaskets int-o sealing engagement with the outer edges of plates l4 and the ends of the casing so as to seal the junctions between the plates and the casing. Compression of the washers also produces expansion of the gaskets, which expansion can take place radially in only one direction. that is outwardly, into tight sealing engagement with the inner walls of caps l2 adjacent the junctions between the caps and the ends of the casing. Thus the gaskets also seal the junctions between the caps and the casing. The tight .engagement between the gaskets and the inner walls of the caps serves also to resist unscrewing of the caps from the casing. The serrations in the peripheries of disks I4 prevent turning of the disks relative to the casing while the closure caps are being screwed on to the casing and thereby prevent damaging twisting of fuse link 13.

From the foregoing, it will be seen that the improved sealing closure of my present invention, while being of very simple and economical form, provides a permanent and reliable sealing of the fuse enclosure against leakage thereinto of liquid insulating medium and at the same time insures a good electric connection between the fuse terminal caps and the fuse link within the fuse enclosure.

Although I have elected to describe and illustrate herein a preferred embodiment of my invention as employed in the construction of a liquid-tight enclosure for a fuse of the inert filler current limiting type, it is contemplated that other applications of the invention, to fuses or like electric devices other than of the particular form illustrated, will suggest themselves to those skilled in the art. It is intended that such other applications or modifications as do not depart from the true spirit of the invention shall come within the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a fuse or like electric device having a housing structure including a tubular casing with an open end and a closure cap secured on said end of the casing; sealing means including a gasket of deformable material and a retaining ring therefor interposed between said cap and a portion of said casing and maintain-ed under compression by said cap to seal said end of the casing, said ring having a generally U-shaped cross-section providing a channel in which the gasket is seated, which said channel opens in a direction substantially normal to the axis of said ring so that said gasket under compression expands in the aforesaid direction into sealing engagement with a surface of said structure extending in opposed relation to said channel.

2. In a fuse or like electric device, including a tubular casing having an open end, a sealing closure for said openend including a closure cap screw-threaded on the casing, an annular washer interposed between said casing and said cap interiorly of the cap and having a generally U- shaped cross-section providing an annular outwardly opening channel, and an annular gasket of deformable material seated in said channel, said washer and gasket being maintained under compression by said cap so as to cause expansion of the gasket substantially radially outward into sealing engagement with the inner walls of said cap adjacent the junction between the cap and easing,

3. In a fuse or like electric device, the combination with a tubular insulating casing member having an open end, a conductive closure cap member in screw-threaded engagement with said end of the tubular member and a disk-like terminal member at said end of the tubular member inwardly of said cap member; of sealing means comprising an annular gasket of deformable material and a metallic retaining ring therefor interposed between said cap member and said terminal member and maintained under compression by the cap member to seal the junctions between said members, said ring having a U-shaped cross-section providing an annular channel in which said gasket is seated and which channel opens in a direction normal to the axis of said ring so that the gasket under compression expands in the aforesaid direction into sealing engagement with a surface of one of said members extending in opposed relation to said channel.

4. In an electric fuse including a tubular casing having an open end, a fuse link attachment plate at said end of the casing; a conductive cap screw-threaded on said end of the casing, an annular metallic washer interposed between said plate and cap and having a generally U-shaped cross-section providing an outwardly opening channel, an annular gasket of deformable material seated in said channel, said washer and gasket being maintained under compression by said cap so as to cause said gasket to expand substantially radially outward int-o sealing engagement with the inner walls of the cap, and means for preventing turning of said plate relative to said casing as said cap is screwed on to the casing.

5. In an electric fuse including a tubular casing having an open end, a terminal cap screwthreaded on said end of the casing, a fuse link attachment plate seated in an annular recess at said end of the casing and having serrations biting into the walls of the recess to prevent turning 'of the plate relative to the casing, an annular gasket of deformable material, and a retaining ring for said gasket having a generally U -shaped cross-section providing an annular outwardly opening channel in which said gasket is seated, which said ring and gasket are interposed between said plate and cap and maintained under compression by the cap so as to cause expansion of the gasket outwardly into sealing engagement with the inner walls of the cap, said gasket having also a portion compressed into sealing relation to the junction between said plate and the casing. 7

ROBERT W. GOFF. 

